The Risks of Cancer Screening

With More Cancer Screening and Earlier Testing, Overtreatment on the Rise

Medically Reviewed by Louise Chang, MD on October 22, 2012

Routine cancer screening can save lives. It can also cause serious harm.

This is the "double-edged sword" of cancer screening, says Otis Webb Brawley, MD, chief medical officer at the American Cancer Society.

"Many of these cancers we treat and cure never needed to be treated and cured," Brawley says. "They are never going to kill that patient."

At the heart of the problem is our justifiable fear of cancer. The message has been drummed into us: Find cancers early while they're still curable and get rid of them. We want out from under the shadow of the dreaded C word.

Not so very long ago, most cancers were in their deadliest, late stages by the time doctors could detect them. That's still true of some kinds of cancer, but with others -- such as breast cancer, colon cancer, cervical cancer, and prostate cancer -- advances in cancer screening now make it possible to find many tumors in their earliest stages.

Some of these early cancers will become killers. Others never will. But there's no reliable way to tell which is which. Doctors feel their hands are forced.

"We are treating lesions that never would come to medical attention were it not for increasingly sensitive medical tests," says Barnett S. Kramer, MD, MPH, associate director for disease prevention at the National Institutes of Health.

Biopsy Harm

Maybe it's already happened to you.

You feel perfectly fine as you walk into the doctor's office for a check-up. You get a routine screening test. Later, you get a call. The test says you may have cancer. You'll need more tests to be sure.

Yesterday you were a healthy person. Today you might be a cancer patient. And you won't find out for sure until you have a bit of your body removed with a needle or scalpel or scope -- a biopsy -- to find out if it's cancer.

Maybe that biopsy didn't hurt much. Maybe it did. Or maybe you're one of the unlucky few who suffered a serious injury, such as a perforated colon or a blood infection.

But now you have a new problem. You anxiously wait for the next call, the one that will tell you whether there really are cancer-like cells in your body.

If it's not cancer, you may breathe a sigh of relief. If it is cancer, you might think the test saved your life. But maybe not.

The vast majority of screening-triggered, cancer-positive biopsies detect cells in the very earliest stages of becoming cancers.

That's good, isn't it? Early-stage cancers usually are curable. But there's a catch, Kramer says.

"Unfortunately, right now we are diagnosing a large number of people without precise enough knowledge to spare those who don't need to be treated from treatment," Kramer says. "We treat them, but we have to accept the possibility that there is overtreatment."

Not All Cancers Kill

In 1924, a Johns Hopkins doctor named Joseph Bloodgood noted that the earlier a cancer was detected, the longer patients survived. In a famous New York Times editorial, he predicted that future cancer screening tests would virtually eliminate cancer by detecting lesions at their earliest stage.

Bloodgood was right that better screening tests would come along. And he was right that earlier diagnosis increases survival, although not always in the way he predicted. Earlier diagnosis may increase the time people live with cancer without necessarily letting them live longer.

But Bloodgood was wrong about eliminating cancer. Cancer rates have fallen since routine screening began, but they haven't dropped off a cliff. Over 1975 to 2007, the U.S. cancer death rate dropped from 200 to 178 deaths per 100,000 people.

Doctors are screening for some of the biggest cancer killers on earth. Screening is routine for cancers of the breast, prostate, colon, and cervix. Smokers get screened for lung cancer. Cure rates are up. Death rates are down -- but not as much as cure rates would predict.

Why? As Brawley notes, many of the cancers we're detecting and curing would never have killed. Some cancers are, or become, benign. Some "spontaneously remit," meaning they go away. Some -- doctors call them "indolent" -- grow so slowly that a person would die of something else.

"Overtreatment is treatment that was not necessary at all because the tumor did not need to be treated," Kramer says. "There is more and more evidence that there is an increasing pool of these tumors."

The Downside of Cancer Treatment

No question: Cancer treatment saves many lives. But it's serious, often involving surgery, toxic drugs, and/or radiation. Treatment can scar and damage bodies, increase the risk of other cancers, and reduce the quality and length of a person's life.

It's worth it if it saves your life. But what if it doesn't? Many people have to accept the risks of routine cancer screening in order for one person to benefit. And when a cancer is found, treatment is no walk in the park.

"We do major surgery. We give radiation, a known carcinogen. We give chemotherapy, also a known carcinogen," Kramer says. "It is difficult to make a healthy person better than they are, and that is the very high bar screening tests must clear."

Yet most doctors would agree that it would be wrong not to treat people with early cancers, says Stefan Gluck, MD, an oncologist at the University of Miami Sylvester Comprehensive Cancer Center.

"With any cancer, even the smallest one can be very aggressive," Gluck says. "I do not believe it is wrong to find cancer early and get rid of it."

Living With Uncertainty: The Limits of Science

Short of a cure, perhaps the greatest unmet need in cancer research is to find tests that tell us which tumors need to be treated.

"What we need to do as scientists is to find better tests. Tests that are more specific, cheaper, not expensive, and five to 15 years later show we are detecting more cancers and less people are dying," Gluck says. "But if the tests detect the same number of cancers and same numbers of people are dying, a test is not effective."

Nearly all patients treated for screening-detected cancers believe their treatment cured their cancer and saved their lives. But many if not most of them never needed to be cured at all. They were overdiagnosed and overtreated.

"Unfortunately right now we are left with diagnosing a large number of people without precise enough knowledge to spare those who don't need to be treated," Kramer says. "And because cancer is such a fearsome disease, we often feel that patients can't tolerate going untreated."

Prostate cancer offers a good example. According to the U.S. Preventive Services Task Force (USPSTF), "A large majority of the men who are being treated would do well without treatment." Yet in the U.S., 90% of these men opt for treatment.

"We have a culture of treating cancers aggressively, but we know all those men don't need to be treated," Kramer says.

Another example is the most feared form of skin cancer: melanoma. Melanoma rates have gone up since the late 1980s. Most of the increase is in early cancers detected as skin-exam screening became more common. But late-stage melanoma cases didn't decline, Kramer says. Neither did the death rate.

Brawley agrees. "I cannot quote a study showing that melanoma screening definitely saves lives," he says. "We cure some melanomas that don't need to be cured."

Nobody wants to live with cancer. Nobody wants to be overdiagnosed or overtreated. It's just that we want -- need -- answers that medical science does not yet have.

"What we really need is a 21st century definition of cancer so we can move away from 20th century screening and diagnosis using an 1840s definition of cancer," Brawley says.

There are limits to science, says Susan G. Fisher, PhD, professor and chair of public health sciences at the University of Rochester, N.Y.

"People are uncomfortable and concerned because they think we are recommending less screening in some groups," she says. "The message for the public is that science is hard. As we get more and more information we get smarter about our advice. The most recent evidence says that in groups at low risk, we are creating more problems than benefits with early screening."

To Screen or Not to Screen?

Some people are at higher risk of cancer than other people. For example, women may have inherited genes that raise their risk of breast cancer. Or they might be a smoker, raising their risk of lung cancer.

For people at risk of cancer, the benefits of screening often outweigh the harms. For those not at risk, deciding on whether to undergo cancer screening can be a close call.

The USPSTF recommends routine screening -- that is, for people at normal risk -- for only three cancers:

  • Breast cancer screening mammography is recommended for all women aged 50 to 74. Women under age 50 must weigh the benefits and harms before deciding to undergo screening mammography.
  • Colon cancer screening is recommended for all adults from age 50 until 75.
  • Cervical cancer screening every three years via Pap smear is recommended for all women aged 21 to 65. At age 30, women may opt for screening every five years with a combination of Pap tests and testing for human papillomavirus (HPV).
  • Groups such as the American Cancer Society and the National Cancer Institute say CT screening should be offered to those at high risk of lung cancer. That includes smokers and former smokers ages 55 to 74 who have smoked for 30 pack-years or more and either continue to smoke or have quit within the past 15 years. A pack-year is the number of cigarette packs smoked each day multiplied by the number of years a person has smoked. Their guidelines are based on research that showed CT screening decreases the chance of death overall but increases the chance of having a false alarm that requires more testing.

The USPSTF says there's not enough evidence to recommend for or against routine screening for bladder, oral, and skin cancers. The panel advises against routine screening for ovarian, pancreatic, prostate, and testicular cancers.

If you're not sure what cancer screenings are recommended for you -- or you're not sure you want to go through with those tests -- talk it over with your doctor. Ask for the pros and cons of testing, in light of your preferences, overall health, and family history.

Show Sources


Barnett S. Kramer, MD MPH, associate director for disease prevention, National Institutes of Health, Bethesda, Md.

Susan G. Fisher, PhD, professor and chair, department of public health sciences, and director, doctoral program in epidemiology, University of Rochester, N.Y.

William Farrar, director, Stefanie Spielman Comprehensive Breast Center, Columbus, Ohio.

U.S. Preventive Services Task Force web site.

National Cancer Institute web site.

American Cancer Society web site.

National Institutes of Health web site.

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